Is it safe for me to take the cover off and look inside?

No. The capacitor behind an LG microwave's high-voltage circuit can still hold a dangerous charge well after the unit has been unplugged, which is exactly why owner checks stop at the outlet, the breaker, whether the door closes fully and whether the turntable is seated correctly - and why the cabinet itself is a technician's job every time.

What does F3 mean on the display?

LG documents F3 specifically as a microwave fault code, separate from the numeric codes used on its ranges and wall ovens even though the format looks similar. It is not a code to try to clear by unplugging and plugging back in repeatedly; if it returns after one reset, the unit needs a proper diagnosis.

I saw a spark inside the microwave. What should I do?

Stop the microwave immediately, unplug it or switch off its breaker, and do not run it again until it has been looked at. Metal trim on a dish or a stray piece of foil can cause a spark on its own, but so can a damaged waveguide cover or an internal fault, and there is no way to tell which from outside the cabinet.

The vent fan on my over-the-range microwave comes on by itself. Is that a fault?

Not necessarily. On many LG over-the-range models the fan starts automatically when it senses heat rising from the cooktop below, to protect the microwave's own controls, and that is expected behavior rather than a malfunction. If the fan keeps running with the cooktop off and cool, the heat sensor or its control is worth testing.

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Microwaves Repair, Done Right the First Time

LG's microwave lineup runs from over-the-range units that also serve as the range hood, to countertop models, to built-in speed ovens installed with a trim kit - different installations, but the same high-voltage components inside that make this strictly a technician's job past the door and the turntable.

LG sells over-the-range, countertop and built-in microwaves, the last of these fitted either as a dedicated speed oven or as a countertop unit set into a trim kit. Over-the-range models are the most involved to service because they double as the range hood – alongside the magnetron, high-voltage diode, capacitor and door switches common to every microwave, they also carry a vent fan, a cooktop light and a heat sensor.

A microwave that runs without heating, trips a fuse repeatedly or will not start with the door closed usually has one failed part in the high-voltage circuit or the door-switch set, and we diagnose it on site with the discharge and cabinet precautions that section of the appliance always needs, regardless of which installation type is in front of us.

Common Microwaves Problems

Microwave running normally but the food staying cold

Unit not starting even with the door fully closed

Sparks or arcing visible inside the cavity

Vent fan or cooktop light not working on an over-the-range model

Turntable not rotating

Keypad buttons not responding, or an F3 code on the display

Microwaves Error Codes

Recognize a code on your display? Look it up before you unplug anything or attempt a repair.

F3

LG Microwave F3 Error Code

See all Error Codes →

Why Trust Us With Your LG Microwaves

Trained on LG microwaves control systems and diagnostics.
Genuine OEM parts stocked for the most common failures.
Upfront flat-rate pricing, approved by you before we start.
30-day workmanship warranty on every repair. Parts may carry the manufacturer's warranty where applicable.

Microwaves Repair, Done Right the First Time

Book Microwaves Repair

Common Microwaves Problems

Microwaves Error Codes

F3

Popular LG Microwaves Models

LG MHES1738F

LG MVEF1337F

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LG MVEL2137D

LG MZBZ1715S

LG LMV2015SB

Why Trust Us With Your LG Microwaves

Microwaves Repair FAQ